Radio system



L. J. WOLF RADIO SYSTEM Oct. 27, 1931.

Filed Nov. 23, 1927 A] no INVENTOR l m J r e S e L A'TToRNEY quencydetermined at a distance.

Patented Get. 27, 1931 UNETED STATES PATENT OFFICE LESTER J. EVOLF, OFSOUTH BEND INDIANA, ASSIGNOP TO WESTINGHOUSE ELECTRIC & MANUFACTURINGCOMPANY, A CORPORATION OF PENNSYLVANIA RADIO SYSTEM Application filedNovember 23, 1927. Serial No. 235,374.

This invention relates to radio systems, and particularly to provisionsfor maintaining, at a predetermined frequency the energy broadcast froma sending station.

5 As explained in my copending application, Serial No. 238,823, filedDecember 9, 1927, assigned to the Westinghouse Electric & ManufacturingComp-any, it is possible to impress upon a radio sending station, a fre-It is also possible to maintain the frequency of a broadcasting stationconstant within narrow limits by means or" a master oscillatorcontrolledby a piezo-electric crystal.

it an object of my invention to combine these two methods of control andprovide means whereby, if one method fails, the other will beautomatically substituted.

It is a further object of my invention to the presence or absence ofoscillations in one frequency-controlling arrangement, for

blocking the crystal-controlled tube when the frequency arrangement justmentioned is op- 5 erative and removing the blocking potential at othertimes.

Other objects of my invention and details of the structure will beevident from the following description and the accompanying' Onev stageof the multiplier is illustrated on the drawin It comprises a vacuumtube 2, the grid of which is supplied from the source 1. The platecurrent of the tube 2 contains ncy of the source 1 is oo low A aparallel-resonant circuit 3, tuned to the frethough only a simpleamplifier 5 is illustrated,

any desired number of amplifiers arranged in cascade may be used.

An inductor 10 and condenser 11 serve to couple the amplifier 5 to' atuned circuit 12, from which a connection 13 extends to the transmittingdevice. The transmitting device may be a. power amplifier or any otherarrangement, the frequency of which is controlled by the frequency inthe circuit 12. 20 provide a grid-biasing device controlled by A vacuumtube 14 is equipped with the frequency-determining piezo-electriccrystal 15. The circuits associating the tube 14 and the crystal 15 areillustrative only. Many circuits by which a vacuum tube generator can becontrolled by crystal are well known and any suitable circuit may beused. The grid of the tube 14 is provided with a grid leak comprising aresistor 16 and a biasing device by which a portion of the potential ofthe battery 8 is impressed on the grid.

The side of the condenser 6 toward the plate circuit of the tube 2 isconnected, through a condenser 17, to the anode of a rectifier 18. Saidanode is connected through a radio-frequency choke coil 19 to the gridof the tube 14.

In the operation of the device, the oscillations from the source 1,whether this source bea receiving set controlled by afrequencydetermining device at a distant station, a tuning fork at theillustrated station, or any other form of frequency-determining device,are impressed upon the tube 2 and amplified thereby. A harmonic of theamplified oscillations is impressed upon the tube 5. The

' tube is nonconducting except during those high-frequency oscillationsare amplified either by the tube 5 alone or, if several stages ofamplification are provided, by each stage thereof, and so reach thetuned circuit 12 and maintain it in oscillation.

. The battery 8 impresses upon the grid of the tube 5 so high a negativebias, that this 5, either directly to the circuit 12 or tothe nextstageof the amplifier. will consist, therefore, of separated impulses,the frequency of which is determined by the frequency of the source 1.They will maintain the :circuit I 12 in oscillation and the decrement ofthe cir cuit. 12 is sufiiciently small to cause'the oscillationsimpressed thereby upon the transmitter, to be substantially uniform.

The connection through the condenser 17 delivers an alternating currentto the rectitube 14 because of the choking action of the coil 19. Thecondenser '17 tends to discharge 1 over a path through the choke 19, theresistor adjusted.

fier 18. The current will pass through the rectifier when a positivepotential is impressed upon the anode thereof, butwill not pass in theopposite direction. A charge will,

therefore, accumulate upon the condenser 17, causing the right handelectrode thereof to become negative. i

The negative potential fromthis condenser Will be impressed, through thechoke coil 19, upon the grid of the tube 14. The individual fluctuationsat the frequency ofth-e circuit 4 will not be impressed upon the grid ofthe 16, the potentiometer at the battery 8, the filament leads, the Bbattery and the inductor of the circuit 4. The leakage over this path issufiiciently slow, because of the high resistance of the grid leak 16,to permit the accumulated charge on the condenser 17 to supplement thepotential impressed upon the gridof the tube 14 by the battery 8.

The potentiometer associated with the, battery 8 permitsthe bias ofthetube 14 to be Preferably this bias, when the condenser 17 is discharged,is only slightly negative sincea vacuum tube oscillation genwith aslightly negative grid. 1 I

When a charge has accumulatedupon the condenser 17, the grid of' thetube '14 is erator of this type Works most effectively stronglynegative. It, therefore, produces a,

jblocking action and prevents the oscillationgenerator 14 from producingany oscillations while the source l'is delivering oscillationstothetube2. a a.

If, from any cause, the oscillation-generator 1 should cease; to deliveroscillations, the

charge will cease to accumulate upon the condenser 17. The leakageaction of the. circuit through the resistor 16 will then becomeeffective and the grid of the tube 14 will assumethe potential derivedfrom the battery 8. This will cause the tube 14 to generateoscillations.

The frequency of the oscillations generated by the tube 14 is determinedbythe crystal 15. Preferably, this crystal is so chosen that thefrequency delivered from the tube 14 to the circuit 12 is very nearlylike that delivered from the tube 5 to the circuit 12. The broadcastingstation, therefore, will continue to send out radiations of nearly thesame frequency when the source 1 is inoperative as it sends whencontrolled by the source 1.

The choke coil19 prevents the oscillations generated by the tube 14 frombeing impressedupon the input of the tube 5. Moreover, because of'thestrongly negative bias of the-tube5', such oscillations as do reach thecondens'er6 from the tube 14 will; be insufficient toproduce anyresult'in the output of the tube 5. If, therefore, thesource 1 and thetube 14 should ever be both oscillating at once, a beat note willnotresult, but the circuit 12 will be controlled by the source 1.

It will, therefore,be evident that the system herein shown will controlthe frequency of the broadcasting station in accordance withthe'frequency from the source 1, as long as said source is operative.The amplifier tube associated with the source 1 insures that when thesourcel is operated even approxi- .mately near to its normal amplitude,the voltages impressedupon the grid of the tube 5 are suflicient toovercome the effect of the battery 8 and render the tube 5 conductive,at least once during each cycle of the harmonic selected by the circuit4. V r e I .When the oscillations impressed on the grid effect upon thetube 14. On the other hand,

when the tube 14 is producing oscillations, so small a fraction thereofwill pass the choke" coil 19, that they will be insufficient to overcomethe biasing effect of the battery 8 and the tube 5 will remainnon-conductive; The

oscillations produced in the circuit 12 cannot be propagated through thetube 5 because they reach it in the non-conductive direction.

Dissipation of the energy from the tube 14,

either inthe circuits to the left of the choke coil 19 or in theamplifier connected with the tube 5 is, therefore, unlikely to occur.

While I have described and illustrated a single embodiment of myinvention, many variations thereof will be evident to those skilled inthe art, and the omission of them from the description is not to beconsidered a limitation. No limitation is intended except such as isrequired by the prior art or indicated-in the accompanying claims.

I claim as my invention: y

1. In a radio system, a transmitting deizo vice, a source oflow-frequency control energy, a frequency multiplying means forproducing a high frequency therefrom and for controlling saidtransmitting device by said high frequency, a second source of highfrequency, means for controlling said transmitting device from saidsecond source and means responsive to the first source for preventingthe second source from producing oscillations.

2. In a radio system, a transmitting device, a master source of periodicenergy, governing means for controlling the frequency of the energy inthe transmitting device in accordance with the frequency from saidmaster source, a second source of periodic energy and connectionswhereby it may control the frequency of the energy in the transmittingdevice, and means for preventing said second source of periodic energyfrom producing oscillations whenever the energy delivered from themaster source exceeds a predetermined minimum, said governing meansincluding a device for preventing energy from the master source fromaffecting the transmitting device when the energy from the master sourceis insuflicint to render said preventing means eflective.

3. In a radio system, a transmitting device, two sources offrequency-controlling energy, means for preventing the generation ofoscillations by one of said sources, and means for preventingoscillations produced by the other source from controlling the frequencyat the transmitting device, and means whereby each of said preventingmeans is effective only when the other is ineffective.

4. In a radio system, a transmitting device, two sources offrequency-controlling energy, means for preventing the generation ofoscillations by one of said sources, and means for preventingoscillations produced by the other source from controlling the frequencyat the transmitting device, and means controlled by the magnitude of theenergy from. one of said sources for determining which preventing meansshall be effective.

5. In a signaling system, a transmitting device, a source offrequency-determining energy therefor, a second source offrequency-determining energy therefor, means responsive to energy fromthe first-mentioned source for rendering the second-mentioned sourceineffective, and means whereby the first-mentioned source is preventedfrom controlling the frequency of said transmitting device if the energydelivered from said source falls below a predetermined minimum.

6. In a signaling system, a transmitting device, a source offrequency-determining energy therefor, a second source offrequency-determining energy therefor, and means responsive to energyfrom the firstmentioned source for so controlling the operation of thesecond-mentioned source that said sources cannot be simultaneouslyeffective to determine the frequency of said transmitting device.

7. In a radio system, two controlling devices for determlnlng acarrler-wave fre- LESTER J. WOLF.

